Blood Gas Analyzers

Blood gas analyzers range in size and weight from quite small, hand- portable systems to larger analyzers that must be transported using a cart. Depending on an analyzer’s capability, the test menu can be customized to include any desired combination of analytes and calculated parameters. Generally, the test menu allows measurement of blood gases, electrolytes, metabolites, and CO-oximetry. Various calculated parameters are also available.

Measurements of blood gases, electrolytes and metabolites utilize a variety of different technologies such as: potentiometery, amperometry and fluorescence. The electrolytes Na+, K+, Ca++, Cl and Mg++ are measured using ion selective electrodes. The hematocrit is measured using conductivity, and hemoglobin concentration can be calculated from this. Hematological parameters are measured using CO- oximetry, based on optical measurements of analytes at a number of wavelengths.

The accuracy and precision of results are related to the strength of the analytical technology, and pre- and post- analytical errors. The quality of results depends on how and by whom the test is performed. Testing in the central laboratory is conducted by appropriately trained personnel who maintain regulatory compliance.

Quality Control is designed to monitor and detect errors in the testing procedure, but generally will not detect errors in sample collection and handling. Quality Control on blood gas analyzers is conducted using individual glass ampoules containing aqueous control solutions, equilibrated with gas mixtures or automatically using onboard quality control materials. Automated QC helps simplify QC procedures and reduce the operator workload, as it can be set to occur at regular intervals.

The clinical performance and characteristics of a system determine its suitability, safety and effectiveness for use. Systems must have high levels of accuracy and precision comparable with reference methods. Other important features are the ability to customize the test menu for a specific location and workload, ease of use, minimal maintenance, and remote troubleshooting.

Scheduled maintenance at set intervals may be required with some blood gas analyzers to change the peristaltic tubes or pump, blood gas cylinders or membranes and electrodes which may require technical support. Regular maintenance and service should be scheduled to occur at times when it is likely to cause least disruption, as during periods of ‘downtime’ the analyzer cannot be used.

Maintenance of single-use cassette systems is minimal, simply requiring visual inspection to ensure they are clean. Cartridge-based, multiple- use blood gas analyzers require additional maintenance to replace reagent pack(s) or the printer paper when necessary. The newer generation of multi-use blood gas analyzers can detect blockages caused by a clotted sample, and either catch or clear the clot automatically, thereby minimizing maintenance time required to resolve the problem.

Test results are often recorded manually, which increases the risk of transcriptional errors and omissions from patient records. Connectivity is the ability of a system or device to connect with other systems or devices to allow data transfer to the hospital or laboratory information systems (HIS or LIS).